How to test your home for radon

Testing is the only way to know your radon level. It is also one of the cheapest home safety checks you can do.

Get a test kit

EPA points to several sources:

• Your state radon program. Some states offer free or discounted kits. Find yours on our state pages.
• National Radon Program Services at Kansas State University, which EPA notes sells discounted kits online.
• Hardware and home stores and online retailers. Choose a kit that includes lab analysis, and follow the directions for mailing it back.
• A credentialed radon measurement professional, who can use continuous monitors. EPA says state programs keep lists of professionals credentialed through a state license or a national proficiency program (NRPP or NRSB).

Short-term or long-term?

• Short-term tests stay in place for 2 to 90 days, often 2 to 4 days for common charcoal kits. They are quick and cheap.
• Long-term tests stay in place more than 90 days and better reflect your year-round average.

EPA’s usual path is a short-term test first, then a follow-up if the result is 4 pCi/L or higher. See short-term vs long-term tests and the follow-up planner.

Where to place the test

EPA’s Citizen’s Guide recommends testing in the lowest level of the home that is used, or could be used, as living space, such as a basement you use or plan to finish, or the first floor if there is no basement. Within that level:

• Put the kit in a room used regularly, but not the kitchen, bathroom, or laundry room (humidity and fans can affect results).
• Place it at least 20 inches above the floor, away from drafts, heat sources, and exterior walls, where it will not be disturbed.
• Keep it away from windows and outside doors.

Closed-house conditions for short tests

For tests shorter than four days, EPA’s guidance is to keep windows and outside doors closed (except for normal coming and going) for at least 12 hours before and during the test. Normal heating and air conditioning can run, but avoid fans that bring in outside air. Do not test during severe storms or unusually high winds, which can change indoor pressure.

Common mistakes

• Opening windows during the test.
• Placing the kit in a humid kitchen or bathroom.
• Forgetting to record start and stop dates and times.
• Letting a mailed kit sit too long before it reaches the lab. Mail it promptly after the test ends.
• Moving the device partway through.

Reading the result

The lab reports your average level in pCi/L. Enter it in our radon level calculator to see how it compares with EPA’s action level of 4 pCi/L and the “consider fixing” range of 2 to 4 pCi/L.

When to retest

EPA suggests retesting after a mitigation system is installed, after major renovations or changes to heating and cooling, if you start using a lower level as living space, and every so often even when earlier results were low.